Monitoring a battery in a portable electronic device

ABSTRACT

The disclosed embodiments provide a system that monitors a battery in a portable electronic device. During operation, the system monitors a state of charge of the battery while the battery is powering the portable electronic device. Next, when the state of charge of the battery reaches a predetermined reserve capacity, the system monitors a voltage of the battery. Then, when the monitored voltage of the battery reaches a predetermined termination voltage, the system puts the portable electronic device into a low power usage state.

RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.13/363,213, entitled “Monitoring a Battery in a Portable ElectronicDevice,” filed Jan. 31, 2012, which claims to U.S. ProvisionalApplication No. 61/533,717, entitled “Remaining State of ChargeIndicator,” filed Sep. 12, 2011, the contents of which applications areentirely incorporated by reference herein.

BACKGROUND

Field

The present embodiments relate to techniques for monitoring a battery.More specifically, the present embodiments relate to techniques formonitoring a battery in a portable electronic device.

Related Art

Typically, the state of charge of a battery in a portable electronicdevice is monitored by a battery gas gauge. The state of charge is thenoften displayed to the user of the portable electronic device so that,among other things, the user can be made aware of the remaining batterylife and can adjust their usage accordingly. The battery state of chargeis also used by the portable electronic device to ensure that the devicecan shut down in an orderly fashion before the battery is no longercapable of powering the device.

However, battery gas gauges typically have some level of inaccuracy whenmonitoring the state of charge of a battery. Therefore, portableelectronic devices usually shut down when the battery gas gaugedetermines that the state of charge of the battery has reached apredetermined reserve capacity. The predetermined reserve capacity isset to be larger than the expected inaccuracies in the battery gas gaugeso that there is always enough remaining state of charge in the batteryto shut down the device in an orderly fashion. However, as a result ofthis, there is often still some usable charge left in the battery afterthe device has shut down. This remaining state of charge is notavailable to the user of the device and hence, in effect, reduces thetotal capacity of the battery which is available to the user.

Hence, use of battery-powered portable electronic devices may befacilitated by monitoring a battery in a portable electronic device toallow use of the reserve state of charge.

SUMMARY

The disclosed embodiments provide a system that monitors a battery in aportable electronic device. During operation, the system monitors astate of charge of the battery while the battery is powering theportable electronic device. Next, when the state of charge of thebattery reaches a predetermined reserve capacity, the system monitors avoltage of the battery. Then, when the monitored voltage of the batteryreaches a predetermined termination voltage, the system puts theportable electronic device into a low power usage state.

In some embodiments, monitoring the state of charge of the batteryinvolves using a battery gas gauge to monitor the state of charge of thebattery.

In some embodiments, when the state of charge of the battery reaches thepredetermined reserve capacity, the method additionally comprisesdisplaying a minimal state of charge value to a user of the portableelectronic device.

In some embodiments, the minimal state of charge value is a 1% state ofcharge.

In some embodiments, when the monitored voltage of the battery has apredetermined number of transient dips equal to or below thepredetermined termination voltage, the system reduces the power drawn bythe portable electronic device from the battery.

In some embodiments, reducing the power drawn by the portable electronicdevice from the battery includes one or more of: reducing the screenbrightness, reducing the speaker volume, and shutting down a radiotransceiver.

In some embodiments, putting the portable electronic device into a lowpower usage state includes putting the portable electronic device into ashutdown state.

In some embodiments, the predetermined reserve capacity is between a 2%state of charge of the battery and a 4% state of charge of the battery.

In some embodiments, the portable computing device includes at least oneof: a smartphone, a tablet computer, and a laptop computer.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A shows a portable electronic device monitoring a battery inaccordance with an embodiment.

FIG. 1B shows two exemplary battery state of charge graphs overlaid ontop of each other to aid in explanation of the operation of anembodiment.

FIG. 2 shows a flowchart illustrating the process of monitoring abattery in a portable electronic device in accordance with anembodiment.

In the figures, like reference numerals refer to the same figureelements.

DETAILED DESCRIPTION

The following description is presented to enable any person skilled inthe art to make and use the embodiments, and is provided in the contextof a particular application and its requirements. Various modificationsto the disclosed embodiments will be readily apparent to those skilledin the art, and the general principles defined herein may be applied toother embodiments and applications without departing from the spirit andscope of the present disclosure. Thus, the present invention is notlimited to the embodiments shown, but is to be accorded the widest scopeconsistent with the principles and features disclosed herein.

The data structures and code described in this detailed description aretypically stored on a computer-readable storage medium, which may be anydevice or medium that can store code and/or data for use by a computersystem. The computer-readable storage medium includes, but is notlimited to, volatile memory, non-volatile memory, magnetic and opticalstorage devices such as disk drives, magnetic tape, CDs (compact discs),DVDs (digital versatile discs or digital video discs), or other mediacapable of storing code and/or data now known or later developed.

The methods and processes described in the detailed description sectioncan be embodied as code and/or data, which can be stored in acomputer-readable storage medium as described above. When a computersystem reads and executes the code and/or data stored on thecomputer-readable storage medium, the computer system performs themethods and processes embodied as data structures and code and storedwithin the computer-readable storage medium.

Furthermore, methods and processes described herein can be included inhardware modules or apparatus. These modules or apparatus may include,but are not limited to, an application-specific integrated circuit(ASIC) chip, a field-programmable gate array (FPGA), a dedicated orshared processor that executes a particular software module or a pieceof code at a particular time, and/or other programmable-logic devicesnow known or later developed. When the hardware modules or apparatus areactivated, they perform the methods and processes included within them.

FIG. 1A shows a portable electronic device monitoring a battery inaccordance with an embodiment. Portable electronic device 100 includesbattery 102 which is coupled to battery monitoring unit (BMU) 104 andthrough current sense resistor 108 to system 106. BMU 104 communicateswith system 106 through communication link 110, and BMU 104 includesbattery gas gauge 112.

Portable electronic device 100 may be any electronic device that ispowered by a battery, including but not limited to a smartphone, atablet computer, a laptop computer, or any other computing device.Battery 102 can be any type of battery capable of powering a portableelectronic device, and can be implemented in any technology. In someembodiments, battery 102 includes more than one separate battery and/orbattery cell.

BMU 104 monitors the voltage of battery 102 and the current flowing outof battery 102 through current sense resistor 108. BMU 104 can beimplemented on a separate processor from system 106 or on the sameprocessor without departing from the invention. Additionally, in someembodiments, BMU 104 and system 106 may share other resources ofportable electronic device 100 such as volatile memory (not shown) ornon-volatile memory (not shown). Note that system 106 may represent allof the other functional portions of portable electronic device 100 nototherwise depicted in FIG. 1A.

Battery gas gauge 112 monitors the state of charge of battery 102 andcan be any process or mechanism implemented in hardware and/or softwarethat can monitor a state of charge of battery 102. In some embodiments,battery gas gauge 112 uses information including but not limited toinformation about the voltage of battery 102, the current drawn frombattery 102, the battery chemistry and cycling history of battery 102,and performance data based on batteries similar to battery 102.Additionally, battery gas gauge 112 stores a value representing apredetermined reserve capacity for battery 102. The predeterminedreserve capacity can be a predetermined value entered by a user ormanufacturer of portable electronic device 100, or any other valuecalculated, entered or otherwise predetermined and used by battery gasgauge 112 as a buffer to account for potential inaccuracies in themonitoring of the state of charge of battery 102 by battery gas gauge112. In some embodiments, the predetermined reserve capacity is storedelsewhere in portable electronic device 100, such as in BMU 104 or insystem 106.

During operation, portable electronic device 100 is powered by battery102. As power is drawn out of battery 102, battery gas gauge 112monitors the state of charge of battery 102. BMU 104 communicates tosystem 106 the state of charge monitored by battery gas gauge 112 minusthe predetermined reserve capacity. System 106 displays the monitoredstate of charge of battery 102 minus the predetermined reserve capacityto a user. In some embodiments, this information is displayed as apercentage of the full state of charge of battery 102 or the full stateof charge of battery 102 minus the predetermined reserve capacity, orany other suitable format that can communicate the relative state ofcharge of battery 102 to a user of portable electronic device 100.

As portable electronic device 100 continues drawing power from battery102, eventually the state of charge of battery 102 monitored by batterygas gauge 112 will fall until it is equal to or less than thepredetermined reserve capacity. When this level is reached, BMU 104communicates to system 106 through communication link 110 that the stateof charge of battery 102 is 1%. Note that BMU 104 could communicate tosystem 106 a value representing any minimal state of charge of battery102 without departing from the invention. For example, BMU 104 couldcommunicate to system 106 that the state of charge of battery 102 is thelowest state of charge above 0% that can be displayed to a user ofportable electronic device 100.

BMU 104 then monitors the voltage of battery 102 and continuescommunicating to system 106 through communication line 110 that thestate of charge of battery 102 is 1% until the voltage measured frombattery 102 by BMU 104 reaches a predetermined termination voltage. Notethat BMU 104 may determine that the voltage measured from battery 102has reached the predetermined termination voltage based on informationincluding but not limited to one or more of the following: the number,duration, or frequency of transient voltage dips that are equal or belowthe predetermined termination voltage, or a steady-state or persistencevoltage measurement equal to or below the predetermined terminationvoltage.

Additionally, in some embodiments, before BMU 104 has determined thatthe voltage from battery 102 has reached the predetermined terminationvoltage, when BMU 104 measures one or more transient voltage dips equalto or below the predetermined termination voltage or some otherpredetermined threshold voltage, BMU 104 signals system 106 throughcommunication link 110 to reduce the power drawn by one or moreresources of portable electronic device 100. For example, after BMU 104has communicated to system 106 that a predetermined number of transientvoltage dips of the voltage from battery 104 are equal to or below thepredetermined termination voltage, system 106 may reduce the power drawnfrom battery 102 through one or more of the following actions: reducingthe brightness of a screen, reducing the volume of speakers, or shuttingdown a wireless communication device such as a radio transceiver.

Furthermore, as BMU 104 measures more transient voltage dips equal tobelow the predetermined termination voltage that exceed otherpredetermined thresholds in number, frequency, or duration, BMU 104 maysignal system 106 through communication link 110 to take additionalactions such as further reducing the screen brightness, or speakervolume, or shutting down one or more other resources of portableelectronic device 100. System 106 may also display a message to a userof portable electronic device 100 to indicate the actions that are beingtaken.

Once BMU 104 has determined that the voltage of battery 102 has reachedthe predetermined termination voltage, BMU 104 communicates a signal tosystem 106 through communication link 110 that causes portableelectronic device 100 to go into a low power usage state. The low powerusage state may include but is not limited to a hibernate state, ashutdown state, or any other state that minimizes or stops further powerfrom being drawn from battery 102. In some embodiments, this signal mayinclude but is not limited to setting a flag that indicates to system106 that portable electronic device 100 should be shut down.

Note that the predetermined termination voltage can be selected by amanufacturer or user of portable electronic device 100, and may beselected so that the voltage from battery 102 is sufficient to allowportable electronic device 100 to enter a low power usage state thatminimizes or stops further power from being drawn from battery 102 in anorderly fashion and without loss of data or other potentiallyundesirable effects on portable electronic device 100. For example, thetermination voltage may be picked to be high enough above the brownoutvoltage for portable electronic device 100 so that even under high loadoperating conditions, portable electronic device 100 can shut down in anorderly fashion before the voltage from battery 102 reaches the brownoutvoltage.

FIG. 1B shows two exemplary battery state of charge graphs overlaid ontop of each other to aid in explanation of the operation of anembodiment. Note that in order to help highlight details of the graphs,the axes of FIG. 1B are not drawn to scale. One graph depicts displayedstate of charge vs. battery capacity curve 122 and uses the verticalaxis displayed state of charge 126 on the left side of FIG. 1B, whilethe other graph depicts battery voltage vs. battery capacity curve 124and uses the vertical axis battery voltage 128 on the right side of FIG.1B.

As described above, during operation of portable electronic device 100,as power is drained from battery 102, the state of charge determined bybattery gas gauge 112 minus the predetermined reserve capacity isreported by BMU 104 to system 106 for display to a user. This isdepicted by displayed state of charge vs. battery capacity curve 122. Asportable electronic device 100 continues to draw power from battery 102,the state of charge of battery 102 monitored by battery gas gauge 112will continue to fall until it is equal to the predetermined reservecapacity. Note that in the embodiments depicted in FIG. 1B, system 106does not display a state of charge of battery 102 to the user that isless than a minimal state of charge (e.g., 1% in this embodiment). Inother embodiments, the minimal state of charge is displayed until theportable electronic device begins to enter a low power usage state.

When battery gas gauge 112 determines that the state of charge ofbattery 102 has decreased to a level that is equal to the predeterminedreserve capacity, BMU 104 continues reporting to system 106 that thestate of charge of battery 102 is 1%. BMU 104 then monitors the voltageof battery 102 as depicted in battery voltage vs. battery capacity curve124. As portable electronic device 100 continues to drain power frombattery 102, the voltage of battery 102 drops until it reachestermination voltage 134. When this occurs, BMU 104 communicates tosystem 106 through communication link 110 a shutdown signal that causesportable electronic device 100 to go into a state that stops furtherpower from being drawn from battery 102. Note that, for convenience,termination voltage 134 on the right axis battery voltage 128 isdepicted as lining up with 0% on the displayed state of charge 126 axis.

In this embodiment, the state of charge of battery 102 between when thevoltage of battery 102 reaches the termination voltage and when batterygas gauge 112 determines the state of charge of battery 102 to be equalto the predetermined reserve capacity (e.g., 0% on the axis displayedstate of charge 126) is represented by reserve state of charge 132 andis available for use by portable electronic device 100.

FIG. 2 shows a flowchart illustrating the process of monitoring abattery in a portable electronic device in accordance with anembodiment. First, the state of charge (SOC) of a battery in a portableelectronic device is monitored (step 202). Then, if the SOC is not lessthan or equal to the predetermined reserve capacity (step 204), theprocess returns to step 202. If the SOC is less than or equal to thepredetermined reserve capacity (step 204), then the process reports thatthe SOC equals 1% (step 206). The battery voltage is monitored (step208), and if it is not less than or equal to the termination voltage(step 210), then the process returns to step 208. If the monitoredvoltage of the battery is less than or equal to the termination voltage(step 210), then the portable electronic device is shut down (step 212).

The foregoing descriptions of various embodiments have been presentedonly for purposes of illustration and description. They are not intendedto be exhaustive or to limit the present invention to the formsdisclosed. Accordingly, many modifications and variations will beapparent to practitioners skilled in the art. Additionally, the abovedisclosure is not intended to limit the present invention.

What is claimed is:
 1. A method for monitoring a battery of anelectronic device, the method comprising: monitoring a voltage of abattery powering an electronic device; reducing power drawn by theelectronic device responsive to satisfaction of a first criteria, thefirst criteria comprising whether a plurality of transient voltage-dipsbelow a predetermined threshold voltage are detected; and furtherreducing power drawn by the electronic device responsive to satisfactionof a second criteria, the second criteria comprising whether a number oftransient voltage-dips below the predetermined threshold voltage perunit time exceeds a predetermined value, wherein the predeterminedthreshold voltage is greater than a brownout voltage.
 2. The method ofclaim 1, further comprising: determining that a predeterminedtermination voltage of the battery has been reached responsive tosatisfaction of a third criteria, the third criteria comprising at leastone of, whether a steady state voltage below the predeterminedtermination voltage has been measured, and whether a persistence voltagebelow the predetermined termination voltage has been measured; and uponsuch determination, placing the electronic device into at least one of ashutdown state and a hibernation state, wherein the predeterminedtermination voltage is greater than the brownout voltage.
 3. The methodof claim 2, the third criteria further comprising at least one ofwhether a number of transient voltage-dips below the predeterminedtermination voltage per unit time exceeds a predetermined value, whethera number of transient voltage-dips below the predetermined terminationvoltage exceeds a predetermined number, and whether a duration of atleast one transient voltage-dip below the predetermined terminationvoltage exceeds a predetermined duration.
 4. The method of claim 3,wherein the predetermined termination voltage is equal to thepredetermined threshold voltage.
 5. The method of claim 4, wherein thepredetermined termination voltage is user selectable.
 6. The method ofclaim 1, wherein reducing power drawn by the electronic device comprisesat least one of reducing a brightness of a screen, reducing a volume ofa speaker, or shutting down a wireless communication device.
 7. Themethod of claim 6, wherein further reducing power drawn by theelectronic device comprises at least one of further reducing thebrightness of the screen, further reducing the volume of the speaker,and shutting down one or more other resources of the electronic device.8. A system for monitoring a battery powering an electronic device, thesystem comprising a voltage monitoring mechanism coupled to the battery,the voltage monitoring mechanism configured to: monitor a voltage of abattery powering an electronic device; reduce power drawn by theelectronic device responsive to satisfaction of a first criteria, thefirst criteria comprising whether a plurality of transient voltage-dipsbelow a predetermined threshold voltage are detected; and further reducepower drawn by the electronic device responsive to satisfaction of asecond criteria, the second criteria comprising whether a number oftransient voltage-dips below the predetermined threshold voltage perunit time exceeds a predetermined value, wherein the predeterminedthreshold voltage is greater than a brownout voltage.
 9. The system ofclaim 8, the voltage monitoring mechanism further configured to:determine that a predetermined termination voltage of the battery hasbeen reached responsive to satisfaction of a third criteria, the thirdcriteria comprising at least one of, whether a steady state voltagebelow the predetermined termination voltage has been detected, andwhether a persistence voltage below the predetermined terminationvoltage has been detected; and upon such determination, place theelectronic device into one of a shutdown state and a hibernation state,wherein the predetermined termination voltage is greater than thebrownout voltage.
 10. The system of claim 9, the third criteria furthercomprising at least one of whether a number of transient voltage-dipsbelow the predetermined termination voltage per unit time exceeds apredetermined value, whether a number of transient voltage-dips belowthe predetermined termination voltage exceeds a predetermined number,and whether a duration of at least one transient voltage-dip below thepredetermined termination voltage exceeds a predetermined duration. 11.The system of claim 10, wherein the predetermined termination voltage isequal to the predetermined threshold voltage.
 12. The system of claim11, wherein the predetermined termination voltage is user selectable.13. The system of claim 8, wherein reducing power drawn by theelectronic device comprises at least one of reducing a brightness of ascreen, reducing a volume of a speaker, or shutting down a wirelesscommunication device.
 14. The system of claim 13, wherein furtherreducing power drawn by the electronic device comprises at least one offurther reducing the brightness of the screen, further reducing thevolume of the speaker, and shutting down one or more other resources ofthe electronic device.
 15. A non-transitory computer-readable storagemedium storing instructions that when executed by an electronic devicecause the electronic device to: monitor a voltage of a battery poweringan electronic device; reduce power drawn by the electronic deviceresponsive to satisfaction of a first criteria, the first criteriacomprising whether a plurality of transient voltage-dips below apredetermined threshold voltage are detected; and further reduce powerdrawn by the electronic device responsive to satisfaction of a secondcriteria, the second criteria comprising whether a number of transientvoltage-dips below the predetermined threshold voltage per unit timeexceeds a predetermined value, wherein the predetermined thresholdvoltage is greater than a brownout voltage.
 16. The non-transitorycomputer-readable storage medium of claim 15, further storinginstructions to: determine that a predetermined termination voltage ofthe battery has been reached responsive to satisfaction of a thirdcriteria, the third criteria comprising at least one of, whether asteady state voltage below the predetermined termination voltage hasbeen measured, and whether a persistence voltage below the predeterminedtermination voltage has been measured; and upon such determination,place the electronic device into one of a shutdown state and ahibernation state, wherein the predetermined termination voltage isgreater than the brownout voltage.
 17. The non-transitorycomputer-readable storage medium of claim 16, the third criteria furthercomprising at least one of whether a number of transient voltage-dipsbelow the predetermined termination voltage per unit time exceeds apredetermined value, whether a number of transient voltage-dips belowthe predetermined termination voltage exceeds a predetermined number,and whether a duration of at least one transient voltage-dip below thepredetermined termination voltage exceeds a predetermined duration. 18.The non-transitory computer-readable storage medium of 17, wherein thepredetermined termination voltage is equal to the predeterminedthreshold voltage.
 19. The non-transitory computer-readable storagemedium of claim 18, wherein the predetermined termination voltage isuser selectable.
 20. The non-transitory computer-readable storage mediumof 15, wherein reducing power drawn by the electronic device comprisesat least one of reducing a brightness of a screen, reducing a volume ofa speaker, or shutting down a wireless communication device.
 21. Thenon-transitory computer-readable storage medium of 20, wherein furtherreducing power drawn by the electronic device comprises at least one offurther reducing the brightness of the screen, further reducing thevolume of the speaker, and shutting down one or more other resources ofthe electronic device.